1. Human-caused climate change is thought to potentially contribute to a sixth mass extinction on Earth for several reasons:
1. Rapid warming is causing shifts in climate zones and the habitats of many species, disrupting ecosystems. Many species may not be able to adapt quickly enough to the rapid pace of climate change.
2. Climate change is exacerbating the effects of other threats like habitat destruction, pollution, and overexploitation. Combined, these threats pose major risks to biodiversity.
3. Climate change is causing changes in weather patterns and an increase in extreme weather events like heatwaves, droughts, wildfires, and floods. These extreme events can decimate populations of plants and animals.
4. Climate change is causing ocean acidification and warming, which damages marine ecosystems like coral reefs and threatens many marine species.
5. Climate change may lead to the emergence of new diseases that can infect wildlife species.
6. Shifts in climate zones may lead to introductions of non-native, invasive species that outcompete native flora and fauna.
So in many ways, climate change acts as a threat multiplier, amplifying the risks to biodiversity from other human impacts. Most experts think substantial reductions in greenhouse gas emissions are urgently needed to avoid catastrophic consequences for many species. Tackling climate change could help preserve far more biodiversity than mitigation efforts focused on any other single threat.
2. Human activities beyond climate change are contributing to risks of sixth mass extinction:
• Habitat destruction and fragmentation: Human activity like land clearing for agriculture, mining, logging, urbanization, and transportation infrastructure is destroying and fragmenting natural habitats around the world. This threatens many species with limited ranges or specialized habitat needs. Tropical rainforests, in particular, support most of the world's species but are being rapidly depleted.
• Pollution: Plastic pollution, toxic chemicals, agricultural runoff, mining waste, and other pollution are degrading habitats, poisoning wildlife, and entering the food supply. Many pollutants also accumulate up the food chain. Pollution has been linked to declining populations of many species like penguins, seals, and sharks.
• Overexploitation: Some species have been overhunted or overfished to the point of endangerment or extinction. Whaling, poaching, and unsustainable commercial fishing have all contributed to the population collapses of various species. Some scientists estimate that overfishing has reduced ocean biomass by over 90% in some areas.
• Agriculture expansion: To feed a growing global population, massive areas of forests, grasslands, and wetlands have been converted to agricultural lands like farms, ranches, and palm oil plantations. This leads to habitat loss, fragmentation, and pollution that undermine biodiversity. Industrial agriculture also relies on pesticides and fertilizers that harm ecosystems.
• Invasive species: As people have moved plants, animals, and crops around the world, some have become invasive in new environments,out-competing native species and damaging ecological communities. Invasive species are a major threat to island biodiversity and vertebrate extinction rates.
• Human population growth: Behind virtually all of these threats is the growth of the human population. More people means more demand for industrialization, pollution, habitat destruction, resource use, and so on—all of which undermine biodiversity. Most experts agree population stabilization is needed to mitigate these threats.
In summary, human activity has caused massive disruption to ecosystems worldwide through multiple, interconnected pressures. Urgent actions are needed across all of these areas to preserve biodiversity and prevent a potential mass extinction event. But the sooner we can curb climate change, the more biodiversity we have a chance to save.